Contact assembly for double-surfaced rectifier elements



C. C; HEIN May 9, 1939.

LE-sunmcn RECTIFIER ELEMENTS Y CONTACT ASSEMBLY F012 'DOUB 2 shuts-sheet 1 Filed Aug. 25, 1938 INVENTOR Carl 6i Hein.

wrrNEssES May 9,: 1939. c. c. HEINy 2,157,895

CONTACT ASSEMBLY Fon DOUBLE-suaAED REGHFI'ER, ELEMENTS Filed 2113.25.' 195e 2 sneetsQ-sheet 2 WITNEssEs: AINVENTOR Car! c. Hem;

WI BY @J4/M2M, L 2 A ORNEY Patented May 9, 193e UNITED *STATES CONTACT ASSEMBLY FOR l-OUBLE-SU?,

AFACED RECTIFIER ELEMENTS Carl C. Hein, Forest Hills, Pasassig'nor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation'o! Pennsylvania y Application august 25,1938, serial 1am--226.646,

4 Claims.

My invention relates to dissymmetrical junctionsfor solid electrical conductors and, in particular, to'electrical rectifiers of the contact type.

One object of my invention is to provide a structure in which electrically conductive plates may form dissymmetrically conductive junctions with coatings of other material covering both of their opposite surfaces.

Another object of my invention is to provide a convenient structure for mounting a pluralityv of plates of the sort described in the preceding paragraph for connection into an electric circuit.

Still another objectof my invention is to provide a convenient, economical and readily manufactured structure for assembling oxidized copper plates to employ both of their opposite surfaces as rectifying junctions in an electrical circuit.

Still another object of my invention is to provide a structure of the type referred to in the two preceding paragraphs in which radial extensions from certain of the plates provide a convenient, economical and readily manufactured means for dissipating heat' either by fluid-stream cooling or by natural convection.

A still further object of my invention is to provide structures of the type referred to in the preceding paragraphs with arrangements for enclosing the dissymmetrical junctions to protect them from contact with the atmosphere-of thel room in which'the apparatus is employed.

Other objects of my invention will become apparent from reading the following description taken in connection with the drawings, in which:

Figure 1 is a View in'mid section and Fig. 2 is an end elevation of a copper oxide rectifier assembly embodying the principles of my invention;

Figs. 3 and 4 are, respectively ..views of opposite sides of a unit assembly of thetype employed in the complete rectifier shown in Figs. 1 and 2, a portion of the plates in Figs. 3 and 4 being shown as cut away. to better illustrate the structural details;

Fig. 5 is a View in section of a modified form of unit assembly which provides for preventing access of the surrounding atmosphere to the oxidized copper plate which forms thefoundation of the rectier unit; and

. Fig. 6 is an end View and Fig. 7' a view in section of a unit assembly suitable to replace the unit shown in Figs. 3, 4 and 5 when it is desired to provide for increased or artificial cooling of the rectiiier.

As is illustrated by basic -Grondahl Patent No. 1,640,335, it has been customary in the past to build copper oxide rectiers by assembling al plug rality of annular oxidized copper washers on a through-bolt. In these assemblies, one side of the copper washer was freed of oxide and constituted one terminal of a disk unit. The otherterminal of each disk unit was a plate of lead` which was pressed into contact with the remaining oxidized side of the disk with considerable force in order to insure good electrical contact thereto. Substantially any desired number of such'washers lo Were mounted on an insulating tube covering the through-bolt, but it was found impracticable to make the outer diameter of the Washers greater than about 11/2 inches, and the latter size has u become pretty much acommercial standard. A single washer of this size could provideadirectlcurrent output of about 0.4 ampere when promuch to be desired as to economy, both of manufacture and cost, and of installation-space, and the arrangement which I describe below makes 25 it possible to obtain rectifiers of substantially higher current output while using but a single through-bolt assembly of rectier disks of larger outsideA diameter. I accomplish this result by substituting for the lead contact .plate on a single side of the copper disk a coating of sprayed metal 'covering a large fraction of both faces of a copper disk in which almost the entire surface has been oxidized. In this Way, I avoid the necessity of maintaining high compressive forces 35 necessary where lead contact plates are used, but nevertheless retain the convenient and readily manufactured circular disk and through-@bolt method of assembly which characterized the earlier types of commercial rectiiiers. 40

With the foregoing principles in mind, Fig. 1 shows a through-bolt l which may be of steel and which is covered with an insulating sleeve 2 of fiber or other desirable insulating material. On this sleeve there are shown as mounted a plu- 45 rality, e. g., four, of individual rectifier units. It will be recognized that the number of such units depends upon the voltage to be rectiiied and that any desired number may be mounted on the above-described through-bolt structure in the 50 same way as are the four units shown in Fig'. 1.

Each of the rectifier units comprises a copper plate 3 which may conveniently be of circular plate 3 may be manufactured by the processes described in the above-mentioned Grondahl Patent No. 1,640,335 and Geiger Patent No. 1,892,382, except that the. oxide l should be formed upon both faces of the copper disk. The central hole of the disk may be slightly eounterbored, at`

least on one side, to remove the oxide lfor a radial distance equal to the thickness of a metal spacing sleeve 5. The opposite faces of the abovedescribed oxidized disk are then coated by a Schoop spray or the like (preferably after application of a coating of colloidal graphite to the oxide surface) with a coating of tin, zinc, silver or other desirable metal. As still another modiiication, the oxide surface may be metalcoated and then be provided with plates 6 of steel, tin or zinc superposed thereon. As will be evident from the end view in Fig. 2 and from the detailed views in Figs. 3v and 4, the metallic coating when used should be applied so as to leave uncovered an annular rim at the outer edge of the disk. On one side of the disk 3, shown in Fig. 4, the plate 6 or the coating is sol formed as to leave an uncovered rim 1 about the central hole, while in the other side of the disk 3 a iishpaper washer 8 may be applied to cover any rim of bare copper which may exist around the central hole, and the plate G'or the sprayed coating is then made to extend radially inward to the edge of the een.

tral hole. As is shown in Fig. 1, this permits the assembly of two (or more) rectifier units on the insulating tube 2 in such a position that the metal sleeves 6 space them apart and make an electrical contact from the central rim I of bare cop-v per on one disk 3 to the metal sheet 6 about the central hole on the adjacent disk unit. An electrical contact-bar 9, sandwiched between the metal sleeves at the middle of the structure, forms a convenient means for conducting current to external circuits from the copper of the middle pair of copper disk units. Four (or any desired even number). of the aforesaid rectifier units having been assembled on the insulating sleeve 2, the through-bolt I may be placed in position with a pair of insulating end sleeves II, end washers I2 and spring washers I3 for rigidly holding the assembly in position when the nut i4 is screwed up.'

In the form shown in Figs. 2, 3 and 4, any desired number, such'as three, spring clips I5 may be used to make contact between the opposite plates 6 (or sprayed metal coatings where the latter alone are used) on each unit assembly, and, if desired, theseclips may be soldered in position to hold each unit together before it is placed in final position on the insulating sleeve 2.

Where it is desired to enclose the copper disk 3 from contact with the atmosphere of the room in which the rectier is to operate, the plates 6 may (except where coating 4 is so thick as to render it unnecessary) have their outer edges bent outward so as to insure that they do not touch the edge of the copper plate 3, and then bent inward so as to touch at their outer periphery. The outer peripheral seam thus produced should be sealed gas-tight, e. g., by soldering it. These covering plates may be alike except that one of them which is contiguous to the side on which the above-mentioned shpaper washer is used should extend radially inward into contact with the insulating sleeve 2, While' the other covering disk should have a central hole larger in diameter than the connecting ring 5, so that it does not make contact with the latter. The metal rings 5 should then each be covered by a ring of insulating material which encloses them from the external atmosphere, and this ring of insulating material should have an outside diameter larger than the inside diameter of the covering plate last mentioned. Alternatively to the use of a ring of insulating material to cover the external surface of the connecting sleeve 5, the latter may be coated with a suitable varnish or lacquer, and such a protecting coating of varnish or lacquer may also be applied to seal the joint ai: each end of the insulating ring when the latter is used as a cover for the connecting sleeve 5. Where the rectifier is intended for use in atmospheres containing acid or other corrosive gases, the surface of the cover plates and of the through-bolt may be covered with a non-corrosive protecting coating.

Where it is desired to provide extra efficient cooling of the rectifier, the plate 6 on the side adjacent the above-mentioned shpaper Washer 8 may be considerably larger in diameter than the copper disk 3. Such a cooling plate may be provided for each unit rectifier and Will furnish a large cooling surface which may make use either of fluid convection ornatural circulation to dissipate the heat generated by current flowing through the rectier. In such a case, the spring clips I5 illustrated in Figs. 2, 3 and 4 may be replaced by single springs I6 fastened at one end to the large diameter cooling plate 6 just described, and at the other end to the plate E on the opposite face of the unit.

Such a unit as is shown in Figs. 1 and 2 constitutes four half-wave rectiers, the terminal 9 acting as a positive terminal for an external circuit when an alternating voltage in impressed from a transformer secondary iI between terminals connected to the sprayed metal coatings or cover plates of the tube and rectier units. Proper circuits for employing rectifier assemblies such as those above described are too well known in the art to require further detailed description.

Plates of other than circular periphery and having more than one through-bolt and lhole therefor are within .the scope of my invention.

To describe one specific embodiment of my invention in detail, the copper plates of Fig. 1 may be of sheet copper .050 inch thick by 4 inches in outside diameter and having a central hole l/2 inch in diameter. The cover plates 6 may be of sheet in about .010-.020 inch thick and 3*/4l inches in outside diameter, the central hole of one set of such plates being of the same diameter as the central hole-in the copper plate 3 and the central hole in the other set of cover plates being about 11/2 inches in diameter. The spring clip I5 may be of steel wire about .050 inch in diameter by 1% total inches long.

In the arrangement of Fig. 5, the dimensions of the copper plate 3 may be the same as those given above for Fig. 1. One cover plate .may have a central hole of the same size as that in the copper plate 3, while the central hole inthe other cover plates may have a diameter of about H; inch. These cover plates may be of the same material and thickness as those already described in' connection with Fig. 1 and may have an outside diameter of about 41/2 inches. The spacing between the edge'of the copper plate 3 and the nearest part thereto of the cover plates 6 should be about .D10-.050 inch. The conducting sleeve 5 may have an external diameter of about inch and a length of about 19g inch. The insulating sleeve I8 in the Fig. 5 modification may have an external diameter of about inch.

tol

aromas It will b e recognized that while I have described my invention as applied to a copper omde rectier, it is equally applicable to copper hemi-sulphide rectiers or to other electrical circuit elements in which it is desired to utilize the properties of a junction between the surface of a disk or plate and a chemically diierent material in contact therewith. In compliance with the patent statutes,y l have described one particular embodiment of my invention, but it will be recognized that the principles thereof are of broader application in ways which will be evident to those skilled in the art. the following claims shall be given the broadest interpretation of which their terms are capable in the light of the prior art.

radially inward to form a hole having substantially the same size as said central hole.

2. A contactrectier assembly comprising a plurality of units ofthe type Specled in claim 1f mounted on an `insulating sleeve through their-central holes, and spacing sleeves of conducting material on said insulating sleeve I, accordingly, desire thatv the copper plate of one sheet of the adjacent unit..

3. A contact rectier assembly comprising a plurality of rectier units, each rectifier unit comprising a circular copper plate having its opposite faces oxidized except for a narrow rim of bare copper surrounding a hole therein, a metallic sheet in contact with each oxidized face of said copper plate except for an insulating rim surrounding said rim of bare' copper, the respective said rectier units being mounted on'an insulating tube which passes through said hole of each of said rectier units, a conductive metal sleeve surrounding said insulating tube between each pair of rectier units and extending from the metallic sheet of one rectier unit to the .hare copper rim of the adjacent rectifier unit,

means for exerting" pressure parallel to the axis of said insulating tube to maintain said rectifler units in position thereon,'and means for making Y connecting the unoxidized 'walls of the hole in unit with the metallic an electrical connection to the Ametal ring be- 

